Table 3 Detected compounds in alkaline-pretreated rice straw slurry with or without oxygen-radical treatment

1

Methoxy oxalic acid

ND

–^a

2

Oxalic acid

1.130 ± 0.232

2.311 ± 0.329

3

Vanillin

3.320 ± 0.541

0.691 ± 0.144

4

Methoxyhydroquinone

ND

0.082 ± 0.029

5

Protocatechuic aldehyde

ND

0.077 ± 0.023

6

4-Hydroxy-6-methoxy-6-oxohexa-2,4-dienoic acid

ND

–

7

3,4-Dihydroxy-5-methoxybenzaldehyde

ND

0.096 ± 0.030

8

4-(2-Methoxy-2-oxoethylidene)pent-2-enedioic acid

ND

–

9

Vanillic acid

0.134 ± 0.052

0.055 ± 0.020

10

Lactic acid

0.502 ± 0.132

0.991 ± 0.203

11

Furfural

0.021 ± 0.003

0.011 ± 0.003

12

HMF

0.010 ± 0.003

ND

13

p-Coumaric acid

2.105 ± 0.478

0.314 ± 0.090

14

t-Ferulic acid

0.687 ± 0.233

0.223 ± 0.044